Each flight log entry usually
represents a launch or test day, and describes the
events that took place.
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Day 48 -
J4 IIIb Crash and Foam Flights with Altimeter

Setting up J4IIIb for a water only,
altimeter flight to compare to foam.

The kids did a great job of helping with the
experiments.

We were only flying the rocket at 110psi to
make sure it stayed within the park. Here it
reached 89m (292') Mostly because it did not go
directly vertically.

Second launch with camera and foam. Again
the rocket went a fair way from the pad and not
straight up.

Although the parachute deployed just past
apogee at 99m (324'), it did not blossom until
25m (84') above the ground.

Third launch of J4IIIb left a great foam
trail.

The parachute failed to open in flight and
the onboard camera failed to record the launch.

Flight computer in the nosecone was
destroyed by the battery behind it. The servo
was also destroyed, the camera separated and
went flying a few meters from impact site and
the altimeter is hanging out.

The altimeter recorded this data. It lost
power on impact and so did not properly store
the remainder of the flight.
max altitude reached: 107m (350')

Graviton launched without a gravity
experiment payload just for fun.

Last landing for the day landed on the car
park about 10 m from the road.

Well finally the weather cleared up and
we were able to get a few launches in this
weekend. We were going to be testing water
vs foam flights using the altimeters, but
one thing lead to another and we just ended
up launching them for fun. Here are the
details of the flight day.

Events

As we arrived at the launch site we
discovered that there was a plague of flies.
With the warm weather we have been having
lately they must have all emerged at the
same time. After 5 minutes of spending more
time swatting them away than setting up the
launcher, dad jumped in the car and went
home to pick up insect repellent. It's good
to live within 2 minutes of the launch site.
As I sprayed myself head to toe with
repellent I began to wonder if I should take
fly-induced drag into account in the rocket
calculations.

Although the first flight pitched over a bit after take off
it came down well under parachute. Max
altitude reached was 89m. We were only
flying the rockets on relatively low
pressure to keep them within the park. We
also set the parachute deploy delay to
half a second later than normal to
minimise drift on the way down.

The only
damage was when the nosecone hit the ground
and the servo motor popped off its mount. We
tried to fix it, but one of the screws
stripped the thread where it was attached
and so we decided to simply swap the entire
payload section we
brought as a backup. This payload also had
an altimeter already mounted and the weight
of the entire section was identical to the
one we replaced.

The nosecone also head
a removable camera mounted in it, so it weighed a
little more and had a bit more drag but we
were going to fly it anyway. We wanted to at
least get some footage with foam, and then
remove the camera for the next flight and
fly a foam comparison mission with an
identical setup to the first water-only
flight.

After the rocket landed everything looked
fine, but we discovered that the camera did
not record anything. I was pretty sure it
was recording when we launched, so I wasn't
too sure what had happened.

We launched it again with the camera
and altimeter. This time the rocket took off
at quite a bit of an angle and headed
straight for the river. The parachute failed
to open and the rocket heavily crashed
through some trees and on the other side of
the river. It took us a few minutes to find
it.

The flight computer was totally
obliterated mostly by the battery that was
located just underneath it. The altimeter was
hanging out the side and the camera had
completely detached and was lying a few
meters away. We checked the camera and
although it turned on, we saw that nothing
was recorded again. Arrrgh! I tried doing a
record test and half way through a recording
the camera just shut itself off. I am not
sure yet if the camera is damaged or perhaps
the battery
might be low. Although we did replace the
batteries recently. We will have to do a few
more tests.

The altimeter survived, and despite
having its power cut on impact still managed
to record almost the entire flight with the
exception of the last few samples. A couple
of the connector pins were bent on it, but
that's all. The servo motor was also
destroyed as the gears are locked together
and you can no longer turn the arm. One of
the fins was also destroyed, and we only
found the base part of it.

We do not know why the parachute failed
to deploy. It is just one of those things I
guess.

We then launched the Graviton rocket a
couple of times since J4IIIb could now easily
fit in the car's glove compartment.
We didn't have a gravity experiment in the
payload but instead just flew it with foam
for the kids. Both flights went well without
incident. We taped the other video camera to
the side of the rocket and ended up with a
semi decent video although the rocket had a
bit of a spin to it.

(If the video does not play, try the latest
Flash player from Macromedia)

What's next?

We are now going to
seriously look at a new nosecone design. We
have been designing the payload section as
lightweight as possible and with the view
that all landings would be gentle. Figuring
if we had a hard landing there wasn't much
we could do anyway, and we would just
rebuild the broken ones. We are now going to
change things quite a bit and allow the
nosecone to come down hard without
destroying anything valuable. With padding and crumple zones it should be able
to protect the rest of the payload better.
It should be relatively simple to then
replace just the outer skin.

The flight computer is also going to get
an upgrade and will be integrated with the
altimeter. Currently I have my hands full
before a launch in setting up the flight
computer to the right time, arming, zeroing
the altimeter, starting the recording,
turning on and starting the onboard video
camera and finally video taping the whole
launch from a distance. A lot of this
happens just before pressurising and the
camera start happens after pressurising so
there is always a danger the rocket could go
bang on the launch pad, when starting it..

If we can get the camera open and gain
access to the switch contacts, I will try to
get the flight computer to switch the camera
to the right mode and start recording,
automatically.

I would like to start the entire process
remotely with an infrared remote control, so
that no one needs to be near the rocket
after it is pressurised. Everything on board
the rocket will be automated. Although this
might take a bit of time to set up, it will
be essential once we start using higher
pressures in our rockets.

Once the nosecone is redesigned we will
get back to comparing the water and foam
flights.

Recording Flights

We are now using a
standardised form for
recording all flights. We used to just write
down the details as they happened, but
sometimes forgot to include everything. The
form also allows us to record the info
quickly and consistently. Although it might
seem like overkill for the hobby, we find it
very useful to go back and refer to previous
flights when we are trying to analyze
performance or when something goes wrong.

We also capture
weather data from the
internet for the closest weather station to
get the environmental data over the course
of the launch day.